Barbara ~ I totally agree with the other ideas what were posted. I would only add to be sure your use dowling or plastic posts between each layer of your cake. And, use the platters that allow you to attach these dowlings to the layers above and below. If you do not use the dowlings, the top layers will more than likely sink into the lower layers.

And, it is good to put some dry powdered sugar between the top of each layer and the bottom of the next tier platter. The powdered sugar enables cut upper layers of the cake to be removed one-by-one without removing all of the frosting from the layer directly underneath.

I always transported tiered cakes separate and assembled them at the site. But, when they were already attached, I transported them whole.

I always put my wedding cakes on 1/2 inch to 3/4 inch plywood (NOT CARDBOARD). And, I fashioned a heavy carboard box for the back of the car to use for transporting... the purpose of the box was only to prevent sliding.

Also, so not try to transport your cake in HOT weather. That is inviting disaster. Transport it at night, if need be.

Take tubes of replacement icing with you for touchup.

Ahhh, yes, I always took a friend with me. Maybe it was to add the laugh factor.

Two people removing the cake from the vehicle and walking inside the building are much, much better than one person doing this.

We always wore comfortable, washable clothes. If we were also to be guests at the event, we took our good clothes and changed AFTER the cake was in place.

One more thought about heat... I saw a pillar wedding cake take a tumble 1/2 hour before a wedding a while back because the bakery had used candy mints to level it. The mints melted in the warm room and down it went! Sooo sad.

Good luck to you.